Question: What chemical compound that's part carbon has the least global-warming potential?
Paraphrase: what chemical has the least greenhouse potency?
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q11173 . ?ent wdt:P2565 ?obj . ?ent wdt:P527 wd:Q623} ORDER BY ASC(?obj)LIMIT 5 
Answer: 1,2-dichloroethane, tetrafluoroethylene, hexafluoropropylene, Novec 1230, methyl bromide